Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-04-27T13:09:17Z No. of bitstreams: 2 Dissertação - Ruimar Calaça de Menezes - 2014.pdf: 3563938 bytes, checksum: 780f3827908c962633ef10e7001a936e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-04-27T13:14:20Z (GMT) No. of bitstreams: 2 Dissertação - Ruimar Calaça de Menezes - 2014.pdf: 3563938 bytes, checksum: 780f3827908c962633ef10e7001a936e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-04-27T13:14:20Z (GMT). No. of bitstreams: 2 Dissertação - Ruimar Calaça de Menezes - 2014.pdf: 3563938 bytes, checksum: 780f3827908c962633ef10e7001a936e (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-03-06 / The objective of this study is to present the Quadratic Function in a new graphic perspective. The Quadratic Function content is taught in the ninth year of elementary school and rst year of high school, the following concepts are learned: equations and inequalities involving polynomials of second degree, graphing, concavity, zeros of the quadratic function, the parable vertex, minimum or maximum and applications in other elds of knowledge. Two mathematical softwares, Winplot and Geogebra, were used in order to facilitate the understanding of graphic representations of functions. The parable was discussed from a historical point of view that also included the concept of speci c terms and de nitions involving functions. The concept of tangent lines to growth and decrease of functions was related. The parable was also exhibited in the context of Analytic Geometry and Calculus, emphasizing the in uence of each coe cient in relation to the graph. The parable was studied as one of the conic sections so studied by Apollonius. Some applications of the parable in daily life, physics and modeling problems were cited. / Este trabalho tem como objetivo apresentar a Fun c~ao quadr atica em uma nova perspectiva gr a ca. O conte udo Fun c~ao Quadr atica e ensinado no nono ano do Ensino Fundamental e primeira s erie do Ensino M edio, sendo trabalhados os seguintes conceitos: equa c~oes e inequa c~oes envolvendo polin^omios de 2o grau, representa c~ao gr a ca, concavidade, zeros da fun c~ao quadr atica, v ertice da par abola, valor m nimo ou m aximo e aplica c~oes em outras areas do conhecimento. Para desenvolver este trabalho, foram utilizados os softwares matem aticos Winplot e Geogebra, com o intuito de facilitar a compreens~ao das representa c~oes gr a cas das fun c~oes. A par abola foi comentada a partir de um contexto hist orico e abrangeu tamb em o conceito de termos espec cos e de ni c~oes envolvendo fun c~oes. Foi relacionado o conceito de retas tangentes ao crescimento e decrescimento das fun c~oes. Tamb em foi exibido a par abola no contexto da Geometria Anal tica e do c alculo diferencial, salientando a in u^encia de cada coe ciente em rela c~ao ao gr a co. A par abola foi estudada como uma das sec c~oes c^onicas t~ao pesquisadas por Apol^onio. Foi citada algumas aplica c~oes da par abola no cotidiano, na f sica e em problemas de modelagem.

A Klippe Carrancas, frente do Sistema de Nappes Carrancas, está posicionada na borda sul do Cráton do São Francisco. A klippe é composta por rochas do Grupo Carrancas e estruturada da base para topo por quartzitos puros a micáceos, gradando verticalmente para estaurolita-granada-cloritóide-clorita filito ou cianita-estaurolita-granada xisto cinza porfiroblástico, dependendo das condições do metamorfismo. O metamorfismo gravado nas rochas aumenta para sudeste, da fácies xisto verde superior, na Serra da Estância, até a transição das fácies anfibolito-eclogito na Serra das Bicas, próximo a cidade de Carrancas. Os mapas metamórficos precedentes indicam a posição da isógrada da estaurolita nas proximidades de Itutinga, extremo leste da Serra do Pombeiro, e a ausência de biotita na Serra de Carrancas. A presente investigação reconheceu, a sudoeste de Itumirim, rochas com paragêneses da fácies xisto verde (cianita + clorita + cloritóide + muscovita + quartzo) e na Serra da Estância da fácies anfibolito inferior, zona da estaurolita, que é alcançada com a quebra do cloritóide em presença de cianita (granada + estaurolita + clorita +muscovita + quartzo ± cloritóide ± cianita). Na Serra do Pombeiro as condições da fácies anfibolito médio são alcançadas com o desaparecimento da clorita. Nas Serras de Carrancas e das Bicas ocorre paragênese da fácies anfibolito médio formada por cianita + estaurolita + granada + quartzo + muscovita. A influência da composição química da rocha no desenvolvimento das paragêneses foi avaliada em modelagem usando pseudosseções nos sistemas químicos KFMASH e MnKFMASH. O Mn aumenta consideravelmente o campo de estabilidade da granada. A previsão das associações minerais presentes no restante da região foi examinada a partir da composição química de algumas amostras, havendo boa concordância com os dados de campo. Aliadas às pseudosseções, técnicas de geotermobarometria, via razões catiônicas e geotermobarometria otimizada, permitiram determinar com boa confiabilidade as condições de metamorfismo para rochas dos dois extremos metamórficos descritos na Klippe Carrancas. Os resultados obtidos da comparação dos campos de estabilidade das paragêneses das amostras no sistema MnKFMASH, com os intervalos P-T da geotermobarometria otimizada forneceram condições de pico metamórfico para a Serra da Estância em 10,0 ±1,7 kbar e 577 ±8°C. Para a Serra das Bicas o pico metamórfico foi alcançado em 12,9 ±1,0 kbar e 608,5 ±19,5°C, com paragênese retro-metamórfica estabilizada em 7,0 ±2,2 kbar e 541,5 ±25,5°C. As associações minerais das amostras estudadas (estaurolita-granada-clorita-cloritóide-muscovita-quartzo - Serra da Estância; cianita-estaurolita-granada-quartzo-cianita - Serra das Bicas) são paragêneses típicas das fácies xisto-verde superior e anfibolito, respectivamente. No entanto, os resultados da geotermobarometria otimizada indicam que as rochas foram expostas a regimes mais elevados de pressão, colocando-as na transição com a fácies eclogito. Como as rochas são pelitos verdadeiros, de composição química restrita, as associações minerais de fácies anfibolito persistem em condições de maior pressão. / The Carrancas Klippe, front of the Carrancas Nappe System, is positioned at the southern edge of the São Francisco Craton. The klippe is composed of rocks from Carrancas Group and is structured from base to top by a pure to micaceous quartzite, grading vertically to a staurolite-garnet-chloritoid- chlorite phyllite or a gray porphyroblastic kyanite-staurolite-garnet schist, depending on the conditions of metamorphism. The metamorphism recorded in these rocks increases to the southeast, from upper greenschist facies in the Serra da Estância to the transition to eclogite facies on Serra das Bicas, nearby Carrancas town. Previous metamorphic maps indicate the position of the staurolite-in isograd near Itutinga town, at far east of the Serra do Pombeiro, and the absence of biotite in the Serra de Carrancas. In this research it was recognized that to the southwest of Itumirim town, the rocks bear greenschist facies paragenesis (kyanite + chlorite + chloritoid + muscovite + quartz) and in Serra da Estância a low amphibolite facies, in the staurolite zone, which is achieved with the breakdown of chloritoid in the presence of kyanite (garnet + staurolite + chlorite + muscovite + quartz ± chloritoid ± kyanite). At Serra do Pombeiro conditions of intermediate amphibolite facies are reached with the disappearance of chlorite. On Serra de Carrancas and Bicas occurs intermediate amphibolites facies paragenesis, formed by kyanite + staurolite + garnet + quartz + muscovite. The influence of bulk composition in the development of some parageneses was evaluated using pseudo-section modelling in KFMASH and MnKFMASH systems. Mn increases the stability field of garnet. The prediction of mineral associations present in the rest of the region was done using the bulk composition of some samples, which show good agreement with field data. Allied to pseudo-sections, isopleth-geothermobarometry and optimal geothermobarometry allowed to determine, with good reliability, the metamorphic peak conditions for rocks of the two metamorphic extremes described in the Carrancas Klippe. The results of comparing the stability fields of the parageneses in the MnKFMASH system of the samples, with P-T intervals from optimal geothermobarometry, provide reliable conditions for the metamorphic peak. In Serra da Estância, peak metamorphic conditions were at 10.0 ± 1.7 kbar and 577 ± 8?. For Serra das Bicas, metamorphic peak conditions were reached at 12.9 ± 1.0 kbar and 608.5 ± 19.5°C, with retro-metamorphic paragenesis stabilized at 7.0 ± 2.2 kbar and 541.5 ± 25.5°C. The mineral associations of the studied samples (staurolite-garnet-chlorite-chloritoid-muscovite-quartz - Serra da Estância; kyanite-staurolite-garnet-quartz-kyanite - Serra das Bicas) are typical parageneses of the greenschist facies and upper amphibolites facies, respectively. However, the results of optimal geothermobarometry indicate that the rocks were exposed to higher pressure regimes, reaching the transition to eclogite facies. Since the rocks are true pelites, with restricted bulk composition, the mineral associations of amphibolite facies persist through conditions of greater pressure.

Westinghouse Electric Sweden AB’s three-dimensional reactor core simulation program POLCA uses a large number of tables containing various fuel dependent data, such as cross sections, pin power maps with power distribution etc. POLCA uses quadratic and linear interpolation to extract the values needed for the simulation. However, finding the correct values to interpolate between takes time. This master thesis describes a method of compacting the tables by removing values, in order to shorten the needed simulation time. This is done so that no significant accuracy is lost in the interpolations. The method also finds deviant values and replaces these with new, interpolated values. The thesis shows that approximately 90 % of all values can be removed without losing significant accuracy. These results are however heavily dependent on the choice of accuracy loss criterion; a lower allowance for accuracy loss lowers the amount of values which can be removed sharply.

Les dimensions des satellites spatiaux tendent à croître fortement alors que le volume disponible dans la coiffe des lanceurs est limité. L'utilisation de structures déployables permet de résoudre cette contradiction. Afin de développer l'offre disponible, le département Recherche de Thales Alenia Space étudie les mètres rubans comme solution innovante de déploiement. La première structure envisagée est un télescope déployé par le déroulement de six mètres rubans assurant également le positionnement du miroir secondaire. D'autres structures déployables utilisant les propriétés des mètres rubans sont également en cours d'étude : mât, panneaux solaires, etc.Il convient alors de se doter d'outils de modélisation spécifiques pour modéliser les scénarios de déploiement et multiplier les configurations envisagées. Deux précédentes thèses ont conduit à l'élaboration de modèles énergétiques de poutre à section flexible, rendant compte du comportement plan des rubans ([Guinot2011]) puis de leur comportement tridimensionnel ([Picault2014]). Cette thèse présente différentes contributions autour de ces modèles de poutre à section flexible. Les hypothèses du modèle ont été améliorées. Le re-positionnement de la ligne de référence sur le barycentre des sections conduit à des résultats plus proches des scénarios physiques (apparition et disparition des plis sur le ruban). A ce jour, les hypothèses et les équations du modèle sont définitivement formalisées. Nous avons établi les équations locales 1D (équilibre, comportement) dans le cas des comportements tridimensionnels avec le souci de la plus grande généralité. Établir ensuite les équations dans des cas dérivés simplifiés (restriction aux comportements 2D, section faiblement courbée) nous a permis d'obtenir un certain nombre de solutions analytiques et les équations à implémenter dans l'outil métier.Nous avons développé sur le logiciel de continuation ManLab les premiers éléments d'un outil métier performant dédié à la modélisation des mètres rubans. Nous avons ainsi pu réaliser deux contributions principales :- Un outil généraliste, performant en temps de calcul, permettant d'étudier les systèmes différentiels 1D (BVP, Boundary Value Problems). Les équations locales des modèles de poutre à section flexible ont été implémentées dans cet outil, avec une discrétisation par interpolation polynomiale et collocation orthogonale.- Un élément fini spécifique pour les poutres à section flexible et son implémentation dans ManLab.Ces éléments ont permis de réaliser différentes simulations numériques conduisant à une meilleure compréhension du comportement des mètres rubans grâce aux diagrammes de bifurcation associés à plusieurs essais significatifs. / Dimensions of spatial satellites tend to grow bigger and bigger, whereas the volume in launchers remains very limited. Deployable structures must be used to meet this contradiction. To expand the offer of possible solutions, the Research Department of Thales Alenia Space is currently studying tape springs as an innovative deployment solution. The first structure to be considered is a telescope that is deployed by the uncoiling of six tape springs that also ensure the positioning of the secondary mirror. Other deployable structures that use the properties of tape springs are under investigation : mast, solar panels,...Specific modeling tools then appear compulsory to model deployment scenarios and multiply the tested configurations. Two previous PhD thesis lead to the development of energetic rod models with flexible cross-sections that account for planar ([Guinot2011])and three dimensional behavior of tape springs ([Picault2014]). This PhD thesis presents several contributions on these rod models with flexible cross-sections. The hypotheses of the model were improved. Re-positioning the reference rod line so that it passes through the sections' centroids leads to results that are closer to experimental scenarios (creation and disappearance of folds in the spring). The hypotheses and equations of the model are now definitively formalized.We have derived the 1D local equations in the three-dimensional behavior case in the most generalist way. Then, the derivation of the equations in simplified cases (restriction to 2D behavior, shallow cross-section) enabled us to obtain several analytic solutions and the equations to implement in the specific modeling tool.We have developed on the continuation software ManLab the first elements towards a home made, efficient modeling tool dedicated to the modeling of tape springs. Two main contributions can be listed :- A generalist tool, efficient in calculus times, to study 1D differential problems (BVP, Boundary Value Problems). The local equations of the rod models with flexible cross sections were implemented in this tool, with a discretization based on polynomial interpolation and orthogonal collocation.- A specific finite element for rods with flexible cross sections and its implementation in ManLab.These elements enabled us to perform several numerical simulations and have a better understanding of the behavior of tape springs thanks to full bifurcation diagrams obtained for significant tests.

Le satellite Herschel Space Observatory a permit de détecter la lumière dans l'infrarouge lointain, ce qui correspond aux fréquences auxquelles émettent les molécules légères lors de leurs transitions rotationnelles. ALMA, un interféromètre situé sur un plateau du désert chilien a pris le relais d'Herschel et va permettre de nouvelles observations des nuages moléculaires froids avec une bonne précision angulaire. ALMA observe dans la gamme du millimétrique et du sub-millimétrique ce qui le rend complémentaire du satellite Herschel (infra lointain). Ces avancées considérables concernant les interactions entre particules au niveau microscopique, permettant de produire et piéger des diatomiques dans des états internes bien précis, ouvrent de nouvelles perspectives dans le domaine de la physique des collisions et de la chimie théorique. L'observation des molécules interstellaires a bénéficié des avancées de la radioastronomie, permettant d'identifier les transitions rotationnelles et vibrationnelles des molécules. De plus, les informations spectroscopiques nous procurent des données importantes sur l’état du milieu interstellaire : ionisé ou neutre.Le cation méthylidène CH+ a été observé dans le milieu diffus par sa transition électronique X1Σ+ -A1Π.Il joue un rôle important dans les différentes étapes du réseau chimique complexe grâce à des processus et réactions moléculaires qui se produisent dans les régions interstellaires et circumstellaires. Donc CH+lance une vaste chaine chimique de processus qui peut évoluer vers la formation d'espèces plus complexes.La transition de structure fine de C+; est la plus forte raie en émission de la voie lactée. L’ion C+ est un traceur de la densité et de la température dans les nuages diffus et les régions dominées par les photons (PDR). La raie de C+ constitue un important outil pour sonder le contenu en gaz et les processus de formation des étoiles dans la Voie lactée et dans d'autres galaxies.Les collisions de C+ avec H2 peuvent mener à la formation de CH+. Cette réaction a été très étudiée théoriquement et expérimentalement, cependant, étant endothermique par 3211cm-1 et, pour les températures typiques du MIS et pour H2 dans son niveau fondamental, la réaction ne se produit pas. Le seul processus est alors le processus d'excitation de spin-orbite de C+.La relaxation spin orbite C+(2P1/2) + H2(v; j) = C+(2P3/2) + H2(v0; j0) qui a été tout d'abord étudiée dans cette thèse contribue au refroidissement du gaz constituant les nuages interstellaires.L'excitation vibrationnelle de H2 (v > 0), qui a lieu lors des collisions avec C+ possède une influence notable sur les abondances de CH+. CH+ est un ion très réactif, il se détruit à partir de la réaction d'abstraction de l'hydrogène qui a été prise en considération dans ce travail. Il est donc intéressant d'évaluer précisément l'efficacité réelle de ce chemin de destruction. Le dilemme est que cet ion est également abondamment trouvé dans le milieu neutre et froid.Ce travail de thèse a comporté des études de collisions inélastiques et réactive d'intérêt interstellaire.Nous avons utilisé les calculs ab initio hautement corrélés. De plus, la dynamique nucléaire des systèmes considérés a été étudiée à l'aide d'un formalisme quantique et indépendant du temps, basé sur les coordonnées hypersphériques : soit inélastique dans le cas de l’excitation spin-orbite de C+(2P) + ortho-H2, et para-H2 et l’excitation rotationnelle de (CD+) + He, ou réactif dans le cas de l’abstraction d’un hydrogène dans H + CH+.Notre soucis a été de donner une base compréhensible des mécanismes et de fournir une quantification des sections efficaces de relaxation spin-orbite et des taux de réaction permettant de remonter aux observations spectroscopiques. Les nouvelles constantes de vitesse que nous avons obtenues devraient aider à mieux interpréter les observations de l'émission de C+ obtenues par les télescopes actuels et futurs. (...) / The Herschel Space Observatory satellite has permitted to detect light in the far infrared, corresponding to frequencies at which molecules emit light through rotational transitions. ALMA, an interferomete rlocated on the Chilean desert of Acatama took over Herschel and will allow new observations of cold molecular clouds with an accurate angular accuracy. ALMA observes in the range of millimeter andsub-millimeter which makes it complementary to the Satellite Herschel (far infrared). These significant advances in observing particle interactions at the microscopic level, to produce and trap diatomic molecules in specific internal states, open new perspectives in the field of collision physics and theoretical chemistry.Observation of interstellar molecules has benefited from advances in astronomy, to identify vibrational rotational ransitions of molecules. Furthermore, spectroscopic data provide us with important information on the state of the interstellar medium: ionized or neutral.The cation methylidene CH + was observed in the diffuse medium through its X1Σ + -A1Π electronictransition. It plays an important role in the different stages of the complex chemical behaviour through processes and molecular reactions that occur in interstellar and circumstellar regions. So CH+ launches large chain chemical processes that can progress to the formation of more complex species.The fine structure transition of C +; is the strongest emission line of the Milky Way. The C + ion is atracer of density and temperature in diffuse clouds and regions dominated by photons (PDR). The C +line is an important tool to probe the gas content and star formation processes in the Milky Way andother galaxies.C+ + H2 collisions can lead to the formation of CH +. This reaction has been extensively studied theoretically and experimentally, however, it is endothermic by 3211cm-1 and at the typical temperatures for MIS and H2 in its ground vibrational state, the reaction does not occur. The only process is then the C + spin-orbit excitation process.Spin orbit relaxation C + (2P1 / 2) + H 2 (v j) = C + (2P3 / 2) + H 2 (v0; j0) which was first studied inthis thesis contributes to the cooling of the gas constituting the interstellar clouds.The vibrational excitation of H2 (v> 0), which takes place during collisions with C + has a significant influence on the abundance of CH +. CH + is a highly reactive ion, it is destroyed by the abstractionreaction of hydrogen that has been considered in this work. It is therefore interesting to accurately assess the effectiveness of this path of destruction. The dilemma is that this ion is also abundantly found in the neutral and cold environment.This thesis focuses on the inelastic and reactive collisions studies of interstellar interest. We used ab initio highly correlated methods to tackle the electronic structure parts. Moreover, the nuclear dynamics of the systems was studied using a time independent quantum formalism, based on the Jacobi coordinates in the case of the spin-orbit excitation of C + (2P) + ortho H2, and para-H2 and rotational excitation of (+ CD) + He, or the hyper spherical coordinates for the reactive process in the case of the abstraction of a hydrogen in H + CH +.Our concern was to give a comprehensive basis of the mechanisms and provide a quantification of the effective spin-orbit relaxation cross sections and reaction rates to confront with spectroscopic observations. The new rate constants we obtained should help to better interpret the observations of C+ radiation emissions obtained by current and future telescopes.

>Magister Scientiae - MSc / The objective of this project is to study the production of Li, Be and B isotopes emitted in the interaction of 12C with 12C at incident energies of 200 and 400 MeV.The energies of these produced fragments were measured with a detector telescope consisting of two silicon detectors at the incident energy of 200 MeV while a third silicon detector was added for the measurements at 400 MeV. / South Africa

No description available.

Structural steel design standards recognize lateral torsional buckling as a failure mode governing the capacity of long span unsupported beams with wide flange cross-sections. Standard solutions start with the closed form solution of the Vlasov thin-walled beam theory for the case of a simply supported beam under uniform moments, and modify the solution to accommodate various moment distributions through moment gradient expressions. The Vlasov theory solution is based on the assumption that cross-sectional distortional effects have a negligible effect on the predicted elastic critical moment. The present study systematically examines the validity of the Vlasov assumption related to cross-section distortion through a parametric study. A series of elastic shell finite element eigen-value buckling analyses is conducted on simply supported beams subject to uniform moments, linear moments and mid span point loads as well as cantilevers subject to top flange loading acting at the tip. Cross-sectional dimensions are selected to represent structural steel cross-section geometries used in practice. Particular attention is paid to model end connection details commonly used in practice involving moment connections with two pairs of stiffeners, simply supported ends with a pair of transverse stiffeners, simply supported ends with cleat angle details, and built in fixation at cantilever roots. The critical moments obtained from the FEA are compared to those based on conventional critical moment equations in various Standards and published solutions. The effects of web slenderness, flange slenderness, web height to flange width ratio, and span to height ratios on the critical moment ratio are systematically quantified. For some combinations of section geometries and connection details, it is shown that present solutions derived from the Vlasov theory can overestimate the lateral torsional buckling resistance for beams.

Lors du traitement d'une tumeur par radiothérapie utilisant des ions comme le 12C, le faisceau peut subir des réactions nucléaires avec les noyaux des tissus menant à la création de particules secondaires plus légères. Cela a pour conséquences de délocaliser une partie de la dose dans les tissus sains et de créer un champ d'irradiation mixte. Afin d'améliorer les connaissances sur la fragmentation du projectile, une expérience a été réalisée par notre collaboration en Mars 2015 au GANIL avec un faisceau de 12C à 50 MeV/n. Cette expérience a permis de mesurer les sections efficaces doublement différentielles en angle et en énergie pour tous les isotopes créés, et ce, sur différentes cibles d'intérêt médical (C, H, O et Ca). Les distributions angulaires et les taux de production ont également été obtenus pour chaque fragment et pour chaque cible. Les résultats ont ensuite été comparés à différents modèles de réactions nucléaire disponibles dans les outils de simulation Monte Carlo GEANT4 et PHITS. Des écarts importants ont été observés avec les résultats expérimentaux, mais aussi entre les différents modèles. Ces conclusions avaient déjà poussé notre collaboration à créer un nouveau modèle, appelé SLIIPIE, spécialisé dans les réactions d'ions légers aux énergies intermédiaires. Les paramètres de ce modèle ont ainsi été ajustés de façon à reproduire au mieux les données expérimentales obtenues. / During the treatment of cancerous diseases using ions such as 12C, the beam will undergo nuclear reactions with the tissues leading to the production of lighter secondary fragments. This tends to delocate a part of the dose into healthy tissues and create a mixed radiation field. In order to improve the knowledge on the projectile fragmentation, an experiment was performed by our collaboration in March 2015 with a 50 MeV/n 12C beam at GANIL. This led to the measurement of double differential cross sections in angle and energy of every isotope created by the fragmentation of carbon on targets of medical interest (C, H, O and Ca). Energy and angular distributions, as well as production rates have also been obtained for every fragment and every target. Experimental data were then compared with nuclear reaction models included in the Monte-Carlo (MC) simulation codes, GEANT4 and PHITS. Important discrepancies were observed with our data, as well as between models. These observations had already led our collaboration in creating a new MC model called SLIIPIE, specialized in intermediate energies reactions with light ions. The parameters of this model were then adjusted in order to best fit the experimental data.

Please read the abstract in the section 00front of this document / Dissertation (MSc)--University of Pretoria, 2003. / Geology / Unrestricted